Re. Converting servos into motors
Hi,
Yes, I've done this. One thing to be careful of, is always remember to test the motors when converted, to ensure they are "balanced" (i.e. both stop at the same pulse width setting). I found out the hard way that this usually isn't the case, and you have to balance them out by adding a small parallel resistor across one side of the errant motor to solve this problem.
Another thing to watch out for is to not pull the motor out of the gears, as they are a pain to put back without damaging the gears/contaminating the grease. This is especially important with the small "aircraft" micro-servos often used in models.
Yours,
-Andre